Postmenopausal women with early-stage estrogen receptor (ER)-positive, HER2-negative breast cancer whose tumors harbor PIK3CA mutations may derive greater benefit from letrozole than tamoxifen monotherapy, especially if a patient has wild-type CCND1 and TP53, according to findings that will be presented at the 2016 San Antonio Breast Cancer Symposium (SABCS).1

Although next generation sequencing has revealed the diverse mutation profiles of ER-positive, HER2-negative breast cancers, the clinical relevance of these findings remains unclear.

Researchers evaluated for molecular alterations in postmenopausal patients with primary breast cancer who received adjuvant letrozole or tamoxifen as part of the phase 3 BIG 1-98 trial (ClinicalTrials.gov Identifier: NCT00004205) and evaluate associations between these alterations and prognosis.

Using next generation sequencing, researchers found that among 538 samples, there were an average of 11 mutations per sample. A quarter of samples had 13 or more mutations; no tumors were without a mutation.

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